1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method and a storage medium.
2. Description of the Related Art
Recent demands for image digitalization have led to the use of digital imaging apparatuses with a function of outputting digital images as radiation imaging apparatuses that capture images of radiation transmitted through an object. In general imaging, apparatuses using an imaging plate that accumulates radiation images as latent images, and flat panel detectors (FPD) for radiation in which phosphors and a large-area amorphous silicon sensor are arranged in tight contact with each other, are in practical use in place of screen-film systems.
In the case of FPD, the electrical characteristics vary with each pixel. Therefore, FPD uses technology for outputting final images after executing correction processing. Pixels having different linearities depending on X-rays incident on FPD are subjected to technology for modeling and correcting the pixels. For example, U.S. Pat. No. 7,632,016 discloses technology for estimating pixel values using models obtained through γ correction.
Japanese Patent Laid-Open No. 2002-034961 discloses a method for appropriately correcting pixel defects even when pixels in the state of signal saturation change each time the imaging is performed.
As to weighting technology used in correction of defective pixels, for example, Japanese Patent Laid-Open No. 2008-18047 proposes a method for correcting defects through distance-based weighting.
Japanese Patent Laid-Open No. 2010-263961 proposes a method for changing temporal and spatial weighting in accordance with the mode of defective pixels in moving/still images.
However, radiation imaging apparatuses suffer from the problem that γ correction is not always performed appropriately because the approximation cannot be performed successfully for models using the dose characteristics of the same pixel (e.g. a saturated pixel value for which the approximation does not succeed).
In view of the above problem, the present invention provides technology that enables formation of high-quality images by controlling the settings for weighting output values of pixels using the input/output characteristics which define a relationship between incident doses and output values of pixels corresponding to the incident doses.